verify-stack surfaced a Flowable 500: delivering messageEventReceived to the Beoordelen task's
execution is wrong — a message boundary event's subscription lives on its own execution. Correlate
instead by the registration's process instance id (recorded at submit): query the execution
subscribed to RegistratieIngetrokken and deliver the message there. Withdrawal moves from
IUserTaskClient to IWorkflowClient.WithdrawProcessAsync; the handler no longer needs a task lookup.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Add an interrupting message boundary event (RegistratieIngetrokken) on the Beoordelen task that
ends the process; the Workflow Client delivers the message to the task's execution, and the
withdraw handler triggers it best-effort after the domain transition (ADR-0014).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
## What & why
First sub-slice of **S-11 · Withdrawal (Flow 3)** (#12). A zorgprofessional can withdraw a still-open registration ("trek aanvraag in"); this sub-slice delivers the **domain transition + endpoint**, mirroring how S-12a shipped the beoordeling decision model on its own (#82).
- `RegistrationStatus.Ingetrokken` (terminal).
- `Registration.Withdraw()` — allowed from INGEDIEND or IN_BEHANDELING, needs no zaak, idempotent, and rejected once the registration has been decided (INGESCHREVEN/AFGEWEZEN).
- `WithdrawRegistration` application handler (load → withdraw → persist; repeated withdrawal is a no-op).
- `POST /registrations/{id}/withdraw` on the domain API.
Demoable: `POST /registrations/{id}/withdraw` → `GET /registrations/{id}` shows `INGETROKKEN`.
Refs #12 (not closing — see below).
## Scope / follow-ups
S-11 is bigger than one slice, so it is split (CLAUDE.md §13), like S-12 was:
- **S-11a (this PR)** — domain withdrawal transition + endpoint.
- **S-11b** — cancel the running Flowable process via a BPMN message event, so a withdrawn case leaves the behandelaar's werkbak.
- **S-11c** — owner-scoped BFF self-service withdraw endpoint + "trek aanvraag in" button + e2e.
Cancelling the Flowable process is deliberately deferred (documented in `WithdrawRegistration`), exactly as the beoordeling's rejection deferred its zaak propagation. #12 stays open until S-11c.
## Definition of Done
- [x] Linked Gitea issue (#12).
- [x] Failing test committed before the implementation.
- [x] Implementation makes the test pass.
- [x] Conventional Commits referencing the issue (`refs #12`).
- [ ] CI green — all Gitea Actions jobs.
- [x] `docker compose up` unaffected (no infra/contract change).
- [x] Docs — none needed for this backend sub-slice; the user-visible demo note lands with S-11c.
- [x] No ADR needed — mirrors existing aggregate/handler/endpoint patterns; no boundary change.
## Notes for reviewers
- Verified locally: `Big.Tests` 89/89 pass; `Big.Api` builds clean.
- The domain trusts its callers (§8.3); owner-scoping by the caller's bsn is enforced at the BFF in S-11c.
Reviewed-on: #88
